Adhesion promotion of metal to laminate with multi-functional molecular system

ABSTRACT

An adhesion promotion composition and method for enhancing adhesion between a copper conducting layer and a dielectric material during manufacture of a printed circuit board. The adhesion promotion composition comprises a multi-functional compound comprising a first functional group and a second functional group, wherein the first functional group is an aromatic heterocyclic compound comprising nitrogen and the second functional group is selected from the group consisting of vinyl ether, amide, thiamide, amine, carboxylic acid, ester, alcohol, silane, alkoxy silane, and combinations thereof.

REFERENCE TO RELATED APPLICATION

This application is a U.S. National Application based on PCT applicationPCT/US2009/037969 filed Mar. 23, 2009, and claims priority to U.S.Provisional Application 61/038,434 filed Mar. 21, 2008.

FIELD OF THE INVENTION

This invention generally relates to improving adhesion between a metalsurface and a dielectric material in the manufacture of electronics.More specifically, the invention relates to a method of improving theadhesion between a metal surface and an organic material and/orimproving the adhesion between a metal surface and a glass fiber.

BACKGROUND OF THE INVENTION

A multilayer circuit board (MLB) has, among other things, a number ofmetal layers defining circuit patterns and a number of insulating layersthere-between. The metal layers defining circuit patterns today aretypically formed from copper, and the insulating layers are typicallyformed from a resinous glass fiber-impregnated (“pre-preg”) dielectricmaterial. These respective layers can have a wide variety ofthicknesses. For example, they can be on the order of only micrometersthick or much thicker.

In manufacturing MLBs, it is desirable to enhance the adhesion betweenthe conducting and insulating layers to avoid delamination in subsequentmanufacturing operations or in service. So called “black oxide”processes had been used for years which created a strongly adherentcopper oxide layer to which an insulating layer would adhere better.Black oxide processes have, for most of the industry, been replaced byprocesses such as described in U.S. Pat. Nos. 5,800,859 and 7,232,478involving formation of an organometallic conversion coating (OMCC).These OMCC processes involve exposing the copper circuit layer to anadhesion promotion solution, which contains various components includingan oxidizer, an inhibitor, and a mineral acid. OMCC processes provide a“structured” surface which allows mechanical adhesion to occur duringthe lamination process. The inhibitor, which is an azole, concentratescopper(I) ion at the surface by forming an insoluble azole-copper(I)complex over the copper surface. The copper(I) ion-based complexprovides better mechanical adhesion to organic laminates than copper(II)oxide. The inhibitor also passivates the copper surface to furtherinhibit copper corrosion.

The PCB industry is migrating away from Pb-containing solders towardlead-free solders as required by the Restriction of Hazardous Substances(RoHS) directive which became law in Europe on Jul. 1, 2006. Pb-freesolders require higher reflow temperatures than Pb-containing solders.For example, typical reflow temperatures range from 260° C. to 270° C.for Pb-free solders, as opposed to 220° C. for Pb-containing solders.The higher temperatures challenge many of the materials utilized for theassembly of electronic components, including current inner-layerprocesses such as OMCC processes. It is thought that delamination ofcopper-laminate composites can occur at the required higher reflowtemperatures due to mismatch of coefficiencies of thermal expansion(CTE) between metals and polymer materials.

The coating industry has also been searching for effective adhesionpromoters to improve the adhesion between organic coatings and metalsubstrates, for example, adhesion of solder mask or liquidphotoimageable solder mask (LPSM) to the surface of a board.

SUMMARY OF THE INVENTION

Briefly, the invention is directed to an adhesion promotion compositionfor enhancing adhesion between a copper conducting layer and adielectric material during manufacture of a printed circuit board. Theadhesion promotion composition comprises a multi-functional compoundcomprising a first functional group and a second functional group,wherein (1) the first functional group is selected from the groupconsisting of an aromatic heterocyclic compound comprising nitrogen andan aliphatic amine, and (2) the second functional group is selected fromthe group consisting of vinyl ether, amide, thiamide, amine, carboxylicacid, ester, alcohol, silane, alkoxy silane, and combinations thereof; asurfactant; an acid; and an alcohol solvent.

The invention is further directed to a process for enhancing adhesionbetween a copper conducting layer and a dielectric material duringmanufacture of a printed circuit board. The process comprises exposingthe copper conducting layer to an adhesion promotion compositioncomprising a multi-functional compound comprising a first functionalgroup and a second functional group, wherein (1) the first functionalgroup is selected from the group consisting of an aromatic heterocycliccompound comprising nitrogen and an aliphatic amine and (2) the secondfunctional group is selected from the group consisting of vinyl ether,amide, thiamide, amine, carboxylic acid, ester, alcohol, silane, alkoxysilane, and combinations thereof, wherein the first functional groupinteracts with the surface of the copper conducting layer to form acopper(I) rich organometallic adhesive film over the surface of thecopper conductive substrate.

Other features of the invention will be in part apparent and in partpointed out hereinafter.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a graph showing a wetting curve of coating applied fromadhesion promotion composition of Example 1.

FIG. 2 is a graph showing a wetting curve of coating applied fromadhesion promotion composition of Example 2.

FIG. 3 is an XPS spectra of the region from 920 to 965 eV for analyzingcopper on the surface of the copper sample for (A) the surface treatedwith the adhesion promotion composition of Example 1, (B) the coatingfrom (A) after reflow, (C) the surface treated with the adhesionpromotion composition of Example 2, and (D) the coating from (C) afterreflow.

DETAILED DESCRIPTION OF THE EMBODIMENT(S) OF THE INVENTION

The present invention is directed to an adhesion promotion compositionand a method of using the composition to treat a metal surface, whichtreatment results in enhanced adhesion between the metal surface and adielectric material. For example, the composition can be used to treat acopper conductive surface, e.g., a copper foil, to promote adhesion toresinous glass fiber-impregnated (“pre-preg”) dielectric material in themanufacture of printed circuit boards. Although this composition findsparticular use in printed circuit board manufacture, includingmanufacture of multi-layer boards, the composition of the invention mayimprove the adhesion between dielectric materials and metal substratesin a variety of applications.

Appropriate dielectric substrate materials that may be treated toimprove adhesion to metal surface (e.g., copper foil) in printed circuitboard manufacture include, for example, glass fiber reinforced epoxyresin substrates (i.e., layers of fibrous materials bonded togetherunder heat and pressure with a thermosetting resin). In printed circuitboard manufacture, the epoxy resins are typically derived from areaction between epichlorohydrin and bisphenol-A. The invention isapplicable to a wide variety of epoxy resins typically used in PCBmanufacture. In general, an epoxy resin substrate comprises acontinuous-filament glass cloth bonded with an epoxy-resin system.Specific examples of epoxy resin substrates include the following: G-10,which is a substrate comprising epoxy resin reinforced with glass fibercloth sheets; FR-4, which is a self-extinguishing substrate similar toG-10; G-11, which is a glass cloth and epoxy mixture; and FR-5, which isa flame-resistant version of G-11. FR-4 substrates can be reinforcedwith ceramic particles, such as those available from Rogers Corporation(Chandler, Ariz.).

Other resins that may be reinforced with glass fiber include acrylicresins, such as polymethyl acrylate and polymethyl methacrylate. Stillother resins include polyphenylene ether, cyanate ester, andbismaleimide/triazine.

Additional dielectric materials which can be substrates includeceramics, glass, Teflon, glass fiber-reinforced Teflon,ceramic-reinforced Teflon, polystyrene, and polyimide (for flexibleboard applications).

Most adhesion promotion compositions known in the art enhance adhesionbetween a metal surface and a pre-preg insulating layer by rougheningthe surface of the metal, thereby rendering the surface of the metalamenable to mechanical adhesion through van der Waal's forces and thelike. The adhesion promotion composition of the present invention doesnot rely solely on mechanical forces to adhere the metal surface andpre-preg insulating layer together. Rather, in one embodiment, theadhesion promotion composition comprises a multi-functional compoundcapable of forming chemical bonds to resinous organic dielectricmaterial typically used in pre-preg insulating layers. In oneembodiment, the adhesion promotion composition comprises amulti-functional compound capable of forming chemical bonds to the glassfibers also typically present in pre-preg insulating layers. In oneembodiment, the adhesion promotion composition comprises more than onesuch multi-functional compound, that is, the adhesion promotioncomposition comprises a mixture of multi-functional compounds. In someembodiments, the adhesion promotion composition comprises two or moremulti-functional compounds, wherein each multi-functional compound iscapable of bonding to the same materials, or each multi-functionalcompound is capable of bonding to different materials. For example, theadhesion promotion composition can comprise a first multi-functionalcompound capable of forming chemical bonds to the resinous organicdielectric material in the pre-preg insulating layer and a secondmulti-functional compound capable of forming chemical bonds to the glassfibers in the pre-preg insulating layer. The multi-functional compoundsbonded to the resinous organic dielectric material and/or glass fibersprovide a strongly adhesive layer or film between the metal surface andpre-preg insulating layer. The adhesive film which forms between themetal surface and pre-preg insulating layer is expected to be moredurable than films which rely solely on mechanical adhesion and moreresistant to delamination at the higher temperatures required for reflowof Pb-free solders.

The multi-functional compounds included in the adhesion promotioncomposition of the present invention comprise a first functional groupand a second functional group. In some embodiments, the multi-functionalcompound comprising additional functional group, i.e., a thirdfunctional group, a fourth functional group, etc. The multi-functionalcompounds of the present invention are therefore bi-functional,tri-functional, tetra-functional, or more. In compounds comprising twoor more second functional groups, the plural second functional groupsmay be the same or different. The two or more second functional groupsmay be capable of bonding to the same types of materials in someembodiments. In some embodiments, the two or more second functionalgroups may be capable of bonding to different types of materials. Thefirst functional group roughens the surface of the metal substrate andforms an organometallic conversion coating over the surface of the metalsubstrate. First functional groups capable of forming organometallicconversion coatings include aromatic heterocyclic compounds comprisingnitrogen. The second functional group is compatible with and bonds toresinous organic dielectric material and/or glass fibers typically usedin pre-preg insulating layers in printed circuit board manufacture.Second functional groups capable of bonding with resinous organicdielectric material and/or glass fibers may be selected from the groupconsisting of vinyl ether, amide, amine, carboxylic acid, ester,alcohol, silane, and alkoxy silane. In some embodiments, the adhesionpromotion compound may comprise a combination of two or more such secondfunctional groups. Preferably, the first functional group and secondfunctional group are non-reactive with each other.

In some embodiments, the first functional group comprises an aromaticheterocyclic compound comprising nitrogen. In some embodiments, thefirst functional group comprises an aliphatic amine. The firstfunctional group interacts with copper(I) ions on the surface of thecopper conducting layer and copper(II) ions in solution. Interactionwith copper(I) ions forms a film comprising insoluble copper(I)-basedorganometallics on the surface of the copper conducting layer, i.e., afilm that has become known as an organometallic conversion coating(OMCC). The first functional groups chelates copper(II) ions insolution. These interactions result in the formation of a protectivefilm on the surface of the copper conductive layer which is enriched incopper(I) ions, thereby increasing the ratio of copper(I) ions tocopper(II) ions on the surface of the copper conducting layer. This filmforms a micro-roughened surface morphology on the conducting copperlayer. This micro-roughened copper surface promotes adhesion with thesubsequently applied pre-preg insulating layer. Although this discussionfocuses on a multi-functional molecule applicable for bonding to coppersubstrates, the multi-functional molecule can form an organometallicfilm over other metal surfaces, such as silver, nickel, iron, cobalt,zinc, and tin.

The aromatic heterocyclic compound comprising nitrogen preferablycomprises a 5-membered aromatic ring (an azole). The ring can besubstituted at a carbon atom, a nitrogen atom, or both. The substituentmay be the second functional group capable of bonding to the resinousorganic dielectric material and/or glass fibers. Preferably, the ring issubstituted with the second functional group at a carbon atom. The ringmay be substituted at a nitrogen atom, but preferably at least onenitrogen atom is available to interact with copper(I) ions andcopper(II) ions in a manner which forms a copper(I) rich organometallicadhesive film over the surface of the metal substrate. Even morepreferably, at least one nitrogen atom is available that is bonded to anacidic hydrogen atom, such that the aromatic heterocycle may becomedeprotonated and the resultant negatively charged aromatic heterocyle isavailable to interact with copper(I) ions and copper(II) ions in amanner which forms a copper(I) rich organometallic adhesive film overthe surface of the metal substrate. The ring may be fused to aromatic orcycloalkyl groups, which may be homocyclic or heterocyclic. In oneembodiment, the aromatic heterocycle comprises a substituted 5-memberedring. In one embodiment, the aromatic heterocycle comprises a 5-memberedring that is fused to a 6-membered ring. Exemplary azoles which can befurther substituted with the second functional group are shown in TableI.

TABLE I Azoles Name Structure Pyrrole (1H-azole)

Benzimidazole (1,3- benzodiazole)

Imidazole (1,3-diazole)

Indazole (1,2- benzodiazole)

Pyrazole (1,2-diazole)

1H-Benzotriazole

1,2,3-triazole

2H-Benzotriazole

1,2,4-triazole

Imidazo[4,5- b]pyridine

Tetrazole

Purine (7H-Imidazo(4,5- d)pyrimidine)

Isoindole

Pyrazolo[3,4- d]pyrimidine

Indole (1H-Benzo[b]pyrrole)

Triazolo[4,5- d]pyrimidine

Benzotriazole is known in the art for its anti-corrosion properties,especially for its ability to protect copper surfaces from corrosion.Preferably, the aromatic heterocyclic compound comprising nitrogen haschemical properties substantially similar to benzotriazole. Withoutbeing bound to a particular theory, it is thought that the pKa of acidic—NH moiety in benzotriazole is advantageous for forming organometalliccorrosion coatings. Benzotriazole has a pKa of about 8.4. Preferably,the aromatic heterocyclic compound has a pKa which is similar tobenzotriazole, for example, the aromatic heterocycle comprising nitrogenhas a pKa within about 3 pH units of benzotriazole, such as betweenabout 5 and about 11, but compounds having pKa slightly outside thisrange are potentially applicable. Preferably, the pKa is between about 5and about 13, such as between about 5 and about 11, such as betweenabout 6 and about 10, more preferably about 7.5 and about 9.0, such as,for example, between about 8.0 and about 8.8. Importantly, the aromaticheterocyclic compound comprising nitrogen interacts with copper(I) ionsand copper(II) ions in a manner which forms a copper(I) richorganometallic adhesive film over the surface of the metal substrate.The aromatic heterocyclic compound comprising nitrogen preferably formsthe organometallic film under strongly acidic conditions typicallyassociated with adhesion promotion compositions and is resistant toacid. Preferred aromatic heterocyclic compounds comprising nitrogenhaving these properties include imidazole, triazole, pyrazole,benzimidazole, purine, imidazo[4,5-b]pyridine, and benzotriazole.

Aromatic heterocycles comprising acidic —NH groups, such as imidazoles,benzotriazoles, and purines, having pKas within the preferred ranges maybecome de-protonated and complex with copper ions, thereby forminginsoluble copper complexes even at the preferred highly acidic solutionshaving pHs below about 1.0. Preferred functional groups such as amidesand carboxylic acids are non-reactive with the aromatic compound. Thesefunctional groups are therefore available for reaction with epoxies andpolyimides under the process conditions typically used for laminatingpre-pregs with copper.

In some embodiments, the multi-functional compound is a substitutedazole fused to a 6-membered aromatic ring. Accordingly, themulti-functional compound can have either of the following generalstructures (Ia) or (Ib):

wherein:

A₁, A₂, A₃, A₄, A₅, A₆, and A₂ are carbon atoms or nitrogen atoms andthe sum of nitrogen atoms from A₁, A₂, A₃, A₄, A₅, A₆, and A₂ is 0, 1,2, or 3;

A₁₁, A₂₂, A₃₃, A₄₄, A₅₅, A₆₆, and A₇₇ are selected from the groupconsisting of electron pair, hydrogen, substituted or unsubstitutedalkyl, substituted or unsubstituted aryl, substituted or unsubstitutedvinyl ether, substituted or unsubstituted amide, substituted orunsubstituted amine, substituted or unsubstituted carboxylic acid,substituted or unsubstituted ester, substituted or unsubstitutedalcohol, and substituted and unsubstituted silane or alkoxysilane; and

at least one of A₁₁, A₂₂, A₃₃, A₄₄, and A₅₅ is selected from the groupconsisting of substituted or unsubstituted vinyl ether, substituted orunsubstituted amide, substituted or unsubstituted amine, substituted orunsubstituted carboxylic acid, substituted or unsubstituted ester,substituted or unsubstituted alcohol, and substituted and unsubstitutedsilane or alkoxysilane.

The description of the vinyl ether, amide, amine, carboxylic acid,ester, alcohol, silane, or alkoxy silane as being substituted orunsubstituted is intended to encompass embodiments wherein the vinylether, amide, amine, carboxylic acid, ester, alcohol, silane, or alkoxysilane is bonded directly to the aromatic heterocyclic compoundscomprising nitrogen, embodiments wherein the vinyl ether, amide, amine,carboxylic acid, ester, alcohol, silane, or alkoxy silane is bondedthrough a linking group typically an alkyl, alkenyl, alkynyl, or arylgroup, and embodiments wherein vinyl ether, amide, amine, carboxylicacid, ester, alcohol, silane, or alkoxy silane is bonded through alinking group that is further substituted with other moieties that areoptionally functional in the sense that they are capable of bonding tothe resinous organic dielectric material and/or glass fiber in apre-preg insulating layer. The vinyl ether, amide, amine, carboxylicacid, ester, alcohol, silane, or alkoxy silane in all of theseembodiments is capable of bonding to the resinous organic dielectricmaterial and/or glass fiber in a pre-preg insulating layer.

In some embodiments, the multi-functional compound is selected fromamong substituted purines, substituted benzotriazoles, and substitutedimidazo[4,5-b]pyridines. Accordingly, the multi-functional molecules canhave the following general structures (II) purines, (III)benzotriazoles, and (IV) imidazo[4,5-b]pyridines:

wherein A₂₂, A₄₄, A₅₅, A₆₆, and A₇₇ are as defined in connection withstructures (Ia) and (Ib).

In some embodiments, the multi-functional compound is a substituted5-membered azole ring that is not fused to any additional ringstructure. Accordingly, the multi-functional compound can have thefollowing general structure (V):

wherein:

A₂, A₃, A₄ and A₅ are carbon atoms or nitrogen atoms and the sum ofnitrogen atoms from A₂, A₃, A₄ and A₅ is 0, 1 or 2;

A₂₂, A₃₃, A₄₄, and A₅₅ are selected from the group consisting ofhydrogen, substituted or unsubstituted alkyl, substituted orunsubstituted aryl, substituted or unsubstituted vinyl ether,substituted or unsubstituted amide, substituted or unsubstituted amine,substituted or unsubstituted carboxylic acid, substituted orunsubstituted ester, substituted or unsubstituted alcohol, andsubstituted and unsubstituted silane or alkoxysilane; and

at least one of A₂₂, A₃₃, A₄₄, and A₅₅ is selected from the groupconsisting of substituted or unsubstituted vinyl ether, substituted orunsubstituted amide, substituted or unsubstituted amine, substituted orunsubstituted carboxylic acid, substituted or unsubstituted ester,substituted or unsubstituted alcohol, and substituted and unsubstitutedsilane or alkoxysilane.

In some embodiments, the first functional group is an aliphatic amineApplicable aliphatic amines include primary amines, secondary amines,and tertiary amines

Exemplary primary amines applicable include aminoethane, 1-aminopropane,2-aminopropane, 1-aminobutane, 2-aminobutane, 1-amino-2-methylpropane,2-amino-2-methylpropane, 1-aminopentane, 2-aminopentane, 3-aminopentane,neo-pentylamine, 1-aminohexane, 1-aminoheptane, 2-aminoheptane,1-aminooctane, 2-aminooctane, 1-aminononane, 1-aminodecane,1-aminododecane, 1-aminotridecane, 1-aminotetradecane,1-aminopentadecane, 1-aminohexadecane, 1-aminoheptadecane, and1-aminooctadecane.

Exemplary secondary amines include diethylamine, dipropylamines,dibutylamines, dipentylamines, dihexylamines, diheptylamines,dioctylamines, dinonylamines, didecylamines, diundecylamines,didodecylamines, ditridecylamines, ditetradecylamines,dihexadecylamines, dioctadecylamines, and others.

Exemplary tertiary amines include triethylamine, tripropylamines,tributylamines, tripentylamine, trihexylamines, triheptylamines,trioctylamines, trinonylamines, tridecylamines, triundecylamines,tridodecylamines, tritridecylamines, tritetradecylamines,trihexadecylamines, trioctadecylamines, and others.

Also applicable are organic functional molecules comprising two or moreamine, such as ethylenediamine, 2-(Diisopropylamino)ethylamine,N,N′-Diethylethylenediamine, N-Isopropylethylenediamine,N-Methylethylenediamine, N,N-Dimethylethylenediamine,1-dimethylamino-2-propylamine, 3-(Dibutylamino)propylamine,3-(Diethylamino)propylamine, 3-(Dimethylamino)-1-propylamine,3-(Methylamino)propylamine, N-Methyl-1,3-diaminopropane,N,N-Diethyl-1,3-propanediamine, and others.

Multi-functional compounds for use in the adhesion promotion compositionof the present invention comprising aliphatic amines as the firstfunctional group are preferably substituted at a carbon atom with thesecond functional groups defined herein. In some embodiments, the secondfunctional group may be bonded to a nitrogen atom on the aliphaticamine. In these embodiments, preferably at least one acidic aminecomprising the moiety, —NH, remains available for forming anorganometallic conversion coating.

The second functional group is compatible with and bonds to resinousorganic dielectric material and/or glass fibers typically used inpre-preg insulating layers in printed circuit board manufacture. Thesecond functional group may be selected from the group consisting ofvinyl ether, amide, amine, carboxylic acid, ester, alcohol, silane, andalkoxy silane. In one embodiment, the second functional group is capableof chemically bonding to epoxy and polyimide resins. Second functionalgroups useful in this regard include vinyl ether, amide, amine,carboxylic acid, ester, and alcohol. The adhesion promotion compositionis applicable to other fields where an organic material is applied to ametal substrate. Accordingly, these second functional groups may bond toorganic materials such as acrylate resins, silicone, and polyurethane.In one embodiment, the second functional group is compatible with andbonds to the glass fibers. The functional groups useful in this regardinclude silane and alkoxy silane. The adhesion promotion composition maycomprise a combination of a multi-functional compound having a secondfunctional group capable of bonding to epoxy and polyimide resins and amulti-functional compound having a second functional group capable ofbonding to glass fibers.

In one embodiment, the second functional group is vinyl ether, which hasbeen found suitable for bonding to acrylate resins. The vinyl ether canhave the following structure (VI):

wherein

Ar represents a moiety comprising an aromatic heterocyclic compoundcomprising nitrogen; and

R₁, R₂, and R₃ are each selected from among hydrogen, a substituted orunsubstituted alkyl, and a substituted or unsubstituted aryl. The alkyltypically comprises between about one and about eight carbon atoms, moretypically between about one and about four carbon atoms, i.e., methyl,ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, andtert-butyl. The aryl typically comprises a phenyl, benzyl, naphthyl, oralkyl substituted versions thereof, i.e., tolyl, xylyl, mesityl. Thevinyl ether may be bonded directly to the aromatic heterocyclic compoundor may be bonded through a linkage, which may be a lower alkyl, such asmethylene, ethylene, or propylene, or an aryl, such as phenyl or benzyl.In a preferred embodiment, R₁, R₂, and R₃ are hydrogen.

Preferred aromatic heterocycles for bonding to vinyl ethers includebenzimidazole, indazole, imidazole, and triazole. Exemplary compoundscomprising vinyl ethers bonded to aromatic heterocycles comprisingnitrogen include the compounds in the following Table II:

TABLE II Multi-functional Compounds Comprising Vinyl Ethers NameStructure 2-(vinyloxy)-1H-benzimidazole

2-(vinyloxymethyl)-1H-benzimidazole

3-(vinyloxy)-2H-indazole

2-(vinyloxy)-1H-imidazole

2-(vinyloxymethyl)-1H-imidazole

3-(vinyloxy)-1H-1,2,4-triazole

In one embodiment, the second functional group is amine, which has beenfound suitable for bonding to epoxy resins and polyimide resins. Theamine can have the following structure (VII):

wherein

Ar represents a moiety comprising an aromatic heterocyclic compoundcomprising nitrogen; and

R₄ and R₅ are each selected from among hydrogen, a substituted orunsubstituted alkyl, and a substituted or unsubstituted aryl. The alkyltypically comprises between about one and about eight carbon atoms, moretypically between about one and about four carbon atoms, i.e., methyl,ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, andtert-butyl. The aryl typically comprises a phenyl, benzyl, naphthyl, oralkyl substituted versions thereof, i.e., tolyl, xylyl, mesityl. Theamine may be bonded directly to the aromatic heterocyclic compound ormay be bonded through a linkage, which may be a lower alkyl, having fromone to four carbons, such as methylene, ethylene, or propylene,butylene, or an aryl, such as phenyl or benzyl, with alkyl linkagegroups being preferred. Preferably, the amine is a primary amine or asecondary amine. In one embodiment, R₄ and R₅ are both hydrogen. In oneembodiment, one of R₄ and R₅ is hydrogen, and one of R₄ and R₅ isphenyl.

Preferred aromatic heterocycles for bonding to amines include purine,benzotriazole, benzimidazole, imidazole, and pyrazole. Exemplarycompounds comprising amines bonded to aromatic heterocycles comprisingnitrogen include the compounds in the following Table III:

TABLE III Bi-functional Compounds Comprising Amines Name Structure6-phenylamino-purine

6-benzylamino-purine

6-methylamine-purine

6-dimethyl-purine

9H-purine-2,6-diamine

α-methyl-N-phenyl-1H- benzotriazole-1-methanamine

2-(2-aminoethyl)benzimidazole

2-(2-aminophenyl)-1H-benzimidazole

Histamine

1-methylhistamine

3-methylhistamine

1-(3-aminopropyl)imidazole

3-amino-pyrazole

In one embodiment, the second functional group is amide or a thiamide,which has been found suitable for bonding to epoxy resins. The amide canhave the following structure (VIII):

wherein

Ar represents a moiety comprising an aromatic heterocyclic compoundcomprising nitrogen

X is an oxygen atom or a sulfur atom; and

R₆ and R₇ are each selected from among hydrogen, a substituted orunsubstituted alkyl, and a substituted or unsubstituted aryl. The alkyltypically comprises between about one and about eight carbon atoms, moretypically between about one and about four carbon atoms, i.e., methyl,ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, andtert-butyl. The aryl typically comprises a phenyl, benzyl, naphthyl, oralkyl substituted versions thereof, i.e., tolyl, xylyl, mesityl. Theamide may be bonded directly to the aromatic heterocyclic compound ormay be bonded through a linkage, which may be a lower alkyl, having fromone to four carbons, such as methylene, ethylene, or propylene,butylene, or an aryl, such as phenyl or benzyl, with alkyl linkagegroups being preferred. In one embodiment, R₆ and R₇ are both hydrogen.

Preferred aromatic heterocycles for bonding to amides and thiamidesinclude purine and benzotriazole. Exemplary compounds comprising amidesand thiamides bonded to aromatic heterocycles comprising nitrogeninclude the compounds in the following Table IV:

TABLE IV Multi-functional Compounds Comprising Amides Name Structure5-acetamide-benzotriazole

8-para-methylbenzamide- purine

Benzotriazole-1- carboxamide

N-(2-propenyl)-1H- benzotriazole-1- carbothiamide

N-phenyl-1H- benzotriazole-1- carboxamide

In one embodiment, the second functional group is a carboxylic acid,which has been found suitable for bonding to epoxy resins and polyimideresins. The carboxylic acid can have the following structure (IX):

wherein Ar represents a moiety comprising an aromatic heterocycliccompound comprising nitrogen. The carboxylic acid may be bonded directlyto the aromatic heterocyclic compound or may be bonded through alinkage, which may be a lower alkyl, such as methylene, ethylene, orpropylene, or an aryl, such as phenyl or benzyl. The carboxylic acid maybe bonded directly to the aromatic heterocyclic compound or may bebonded through a linkage, which may be a lower alkyl, having from one tofour carbons, such as methylene, ethylene, or propylene, butylene, or anaryl, such as phenyl or benzyl, with alkyl linkage groups beingpreferred.

Preferred aromatic heterocycles for bonding to carboxylic acids includebenzotriazole, imidazole, and pyrazole. Exemplary compounds comprisingcarboxylic acids bonded to aromatic heterocycles comprising nitrogeninclude the compounds in the following Table V:

TABLE V Multi-functional Compounds Comprising Carboxylic Acids NameStructure Benzotriazole-4-carboxylic acid

Benzotriazole-5-carboxylic acid

Imidazole-4-acetic acid

1H-pyrazole-4-carboxylic acid

1H-pyrazole-5-carboxylic acid

In one embodiment, the second functional group is ester. The ester canhave the following structures (Xa) or (Xb):

wherein

Ar represents a moiety comprising an aromatic heterocyclic compoundcomprising nitrogen; and

R₈ and R₉ are selected from among hydrogen, a substituted orunsubstituted alkyl, and a substituted or unsubstituted aryl. The alkyltypically comprises between about one and about eight carbon atoms, moretypically between about one and about four carbon atoms, i.e., methyl,ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, andtert-butyl. The aryl typically comprises a phenyl, benzyl, naphthyl, oralkyl substituted versions thereof, i.e., tolyl, xylyl, mesityl. Theester may be bonded directly to the aromatic heterocyclic compound ormay be bonded through a linkage, which may be a lower alkyl, having fromone to four carbons, such as methylene, ethylene, or propylene,butylene, or an aryl, such as phenyl or benzyl, with alkyl linkagegroups being preferred. In one embodiment, the ester is structure (V),and R₈ is a methyl group.

Preferred aromatic heterocycles for bonding to esters includebenzotriazole and imidazole. Exemplary compounds comprising estersbonded to aromatic heterocycles comprising nitrogen include thecompounds in the following Table VI:

TABLE VI Multi-functional Compounds Comprising Esters Name StructureMethyl 1H-benzotriazole- 1-carboxylate

Phenyl 1H-1,2,3- benzotriazole-5- carboxylate

1-(benzyloxycar- bonyl)benzotriazole

1H-imidazole-4,5- dicarboxylic acid dimethyl ester

In one embodiment, the second functional group is an alcohol, which hasbeen found suitable for bonding to epoxy resins. The alcohol can havethe following structure (XI):

Ar—OH  (XI)

wherein Ar represents a moiety comprising an aromatic heterocycliccompound comprising nitrogen. The alcohol may be bonded directly to thearomatic heterocyclic compound or may be bonded through a linkage, whichmay be a lower alkyl, having from one to four carbons, such asmethylene, ethylene, or propylene, butylene, or an aryl, such as phenylor benzyl, with alkyl linkage groups being preferred.

Preferred aromatic heterocycles for bonding to alcohols includebenzotriazole, benzimidazole, imidazole, and pyrazole. Exemplarycompounds comprising alcohols bonded to aromatic heterocycles comprisingnitrogen include the compounds in the following Table VII:

TABLE VII Multi-functional Compounds Comprising Alcohols Name Structure4-hydroxy-1H-benzotriazole

2-(2-hydroxy- phenylbenzotriazole

2-(2-hydroxy-5- methylphenylbenzotriazole

1H-Benzotriazole-1- methanol

5-hydroxy-benzimidazole

4(5)- (hydroxymethyl)imidazole

1-(2-hydroxyethyl)imidazole

4-(imidazol-1-yl)phenol

3-hydroxy-1H-pyrazole

5-hydroxy-1H-pyrazole

In one embodiment, the second functional group is a silane or alkoxysilane. The silane or alkoxysilane can have the following structure(XI):

wherein

Ar represents a moiety comprising an aromatic heterocyclic compoundcomprising nitrogen; and

R₁₀, R₁₁, and R₁₂ are independently selected from among hydrogen, alkylgroups having between one and three carbons, alkoxy groups havingbetween one and three carbons, and alkylcarboxyl groups having betweenone and three carbons. The silane or alkoxy silane may be bondeddirectly to the aromatic heterocyclic compound or may be bonded througha linkage, which may be a lower alkyl, having from one to four carbons,such as methylene, ethylene, or propylene, butylene, or an aryl, such asphenyl or benzyl, with alkyl linkage groups being preferred. Preferredsilanes/alkoxy silanes include propyltriethoxysilane,propyltrimethoxysilane, propylmethyldiethoxysilane, andpropylmethyldimethoxysilane.

Preferred aromatic heterocycles for bonding to silanes and alkoxysilanes include benzotriazole and imidazole. Exemplary compoundscomprising alcohols bonded to aromatic heterocycles comprising nitrogeninclude the compounds in the following Table VIII:

TABLE VIII Multi-functional Compounds Comprising Silanes Name Structure1-(Trimethylsilyl)-1H-benzotriazole

1-[(trimethylsilyl)methyl] benzotriazole

1-(trimethylsilyl) imidazole

1-(tert-butyldimethylsilyl) imidazole

The multi-functional compound may added to an adhesion promotioncomposition in a concentration between about 50 g/L and about 0.05 g/L,preferably between about 10 g/L and about 1 g/L.

The above-described multi-functional compounds are typically sparinglysoluble in water. Accordingly, the adhesion promotion composition of thepresent invention may comprise a supplemental alcohol solvent to enhancethe solubility of the multi-functional molecules. Exemplary alcohols foruse in the adhesion promotion compositions of the present inventioninclude diols, triols, and higher polyols. Suitable alcohols includeethanol, n-propanol, isopropanol, 1-butanol, 2-butanol, tert-butanol,iso-butanol, 1-pentanol, 2-pentanol, other pentanols, 1-hexanol, otherhexanols, heptanols, 1-octanol, 2-octanol, and other octanols, 1-decanoland other decanols, phenol, benzyl alcohol, ethylene glycol,propane-1,2-diol, butane-1,2-diol, butane-1,3-diol, butane-1,4-diol,propane-1,3-diol, hexane-1,4-diol hexane-1,5-diol, hexane-1,6-diol,2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, 2-butoxyethanol,1-methoxy-2-propanol, 3-methoxy-1-propanol, 3-ethoxy-1-propanol, etc.Then there are unsaturated diols, such as butene-diol, hexene-diol, andacetylenics such as butyne diol. A suitable triol is glycerol.Additional alcohols include triethylene glycol, diethylene glycol,diethylene glycol methyl ether, triethylene glycol monomethyl ether,triethylene glycol dimethyl ether, propylene glycol, dipropylene glycol,allyl alcohol, furfuryl alcohol, and tetrahydrofurfuryl alcohol.

The alcohol may be present in the composition at an initialconcentration of at least about 10 mL/L. Typically, the concentration ofthe alcohol is at least about 100 mL/L, more typically at least about150 mL/L. The alcohol may be present in the composition at aconcentration up to its solubility limit in water. It is within thescope of the invention to employ solvent systems comprised entirely ofalcohol. In aqueous solvent systems wherein the alcohol is asupplementary solvent, the concentration of the alcohol may be as muchas about 750 mL/L, about 650 mL, or less, such as about 600 mL/L orabout 500 mL/L, more typically less than about 200 mL/L. Accordingly,the alcohol concentration may be between about 10 mL/L and about 750mL/L, typically between about 150 mL/L and about 500 mL/L

In addition to the above-described components, the adhesion promotioncomposition may optionally comprise an oxidizing agent and an inorganicacid. Additionally, the adhesion promotion composition may comprisesurfactants to further enhance the solubility of the multi-functionalmolecules and to aid in cleaning the metal surface. The adhesionpromotion composition of the present invention may also comprise asource of transition metal ion and a source of halide.

In one embodiment, the oxidizing agent is hydrogen peroxide. Hydrogenperoxide may be present in the adhesion promotion composition at aconcentration of at least about 1 wt. %. The concentration of hydrogenperoxide is typically no greater than about 20 wt. %, and in certainpreferred embodiments, it is no greater than about 10 wt. %. In oneembodiment, the concentration of hydrogen peroxide is between about 0.5%by weight of the adhesion promotion composition and about 4% by weight.It has been found that when the concentration of hydrogen peroxide inthe adhesion promotion composition is too high the structure of theroughened surface of the conducting layer forms a somewhat dendriticstructure which is more fragile than the desired roughening effect, sothat it forms a weaker bond than when lower concentrations of hydrogenperoxide are used. Moreover, a high hydrogen peroxide concentration maycause the OMCC to become hazy due to over-etching. All concentrationsare normalized such that they refer to concentrations of each element asif used in 100% concentrations. For example, in one embodiment the H₂O₂solution added to the composition is 35% concentrated H₂O₂, rather thana 100% concentrated H₂O₂. However, the concentrations in the finalcomposition are based on wt. % from 100% H₂O₂, not wt. % of 35% H₂O₂ inthe final composition.

The adhesion promotion composition may comprise one or more inorganicacids for the main purpose of enhancing the solubility of copper andmaintaining other components of the composition in solution. A varietyof acids, such as mineral acids including phosphoric acid, nitric acid,sulfuric acid, and mixtures thereof are workable. In a preferredembodiment, both HNO₃ and H₂SO₄ are employed. It has been discoveredthat in addition to enhancing the solubility of the Cu, H₂SO₄ helps tomoderate the etch rate, and therefore help prevent over-etching of thesubstrate in isolated areas. The HNO₃ increases the etch rate, increasesthe solubility of Cu, helps prevent premature sludge formation, andworks with H₂O₂, H₂SO₄, and the multi-functional compound to darken thecoating. The overall acid concentration in the composition is generallyat least 1 wt. %, preferably at least 8 wt. %, and in certain preferredembodiments at least 14 wt. % of the composition. The etch rate isslowed excessively if the acid concentration is too high, with theexception of nitric acid, and can yield an organometallic conversioncoating which is non-uniform and too light in color. For this reason,the acidity level in previous compositions had been typically selectedto be about 20 wt. %. However, in the present invention it is possibleto push the acidity level up to about 25 wt. % and above, because withthe other additives described herein, the coating is not lightened aswould otherwise be expected with an acid level elevated to about 25 wt.%. The overall acid level is typically maintained below about 50 wt. %.In one preferred embodiment, therefore, there is between about 22 wt. %and about 28 wt. % acid, including about 20 wt. % H₂SO₄ (50% grade) andabout 5 wt. % HNO₃ (95% grade). In one preferred embodiment, theinorganic acid constitutes at least about 30 wt. % of the composition.Another preferred embodiment employs 28 wt. % H₂SO₄ (50% grade) and 5wt. % HNO₃ (95% grade). HNO₃ is employed in these preferred embodimentsbecause it has been discovered that it has a unique ability tosolubilize the inhibitor-Cu complex better than other mineral acids. Thehigh inorganic acid concentrations yield solutions have strongly acidicpH, such as below about 2.0, preferably below about 1.0. While thesepercentages above are percentages of the acids in the final compositionand are based on use of 100% concentrated acid, as discussed above, thepreferred forms of the acids actually added are 50% concentrated H₂SO₄and about 95% concentrated HNO₃.

One embodiment of the invention employs a sulfonated anionic surfactant.It has been discovered that in addition to surface wetting, thissurfactant helps to stabilize the H₂O₂. The most particularly preferredof such surfactants is dodecylbenzene sulfonic acid (DDBSA) or thesodium salt of dodecylbenzene sulfonic acid. DDBSA is commerciallyavailable as the acid or the sodium salt from, for example, AshlandDistribution Company (Santa Ana, Calif.) or from Pilot Chemical Companyof (Santa Fe Springs, Calif.) under the trade designation Calsoft LAS99. Sodium dodecylbenzene sulfonate is also commercially available fromWitco Corporation, Organic Division, (New York, N.Y.) under the tradedesignation Witconate 1850. Additional surfactants include isopropylamine branched alkyl benzene sulfonate available from Stepan Company(Northfield, Ill.) under the trade designation Polystep A-11; and TEAdodecylbenzene sulfonate available from Norman, Fox & Company (Vernon,Calif.) under the trade designation Norfox T-60. This surfactant is usedin a quantity sufficient to achieve surface wetting and H₂O₂stabilization, which quantity can vary depending on the overallcomposition of the adhesion promoter. One currently preferred embodimentincludes at least about 0.0001% of sulfonated anionic surfactant. As ageneral proposition, the sulfonated anionic surfactant concentration isat least about 0.005%, preferably at least about 0.1%; and is less thanabout 10%, preferably less than about 5%, more preferably less thanabout 2%. One specific example employs 0.002% of surfactant,particularly DDBSA.

A currently preferred embodiment of the invention also incorporates asulfated anionic surfactant. One preferred example of this compound issodium 2-ethylhexyl sulfate, also known as 2-ethylhexanol sulfate sodiumsalt, having the formula C₄H₉CH(C₂H₅)CH₂SO₄ ⁻Na⁺. This is available fromNiacet Corporation (Niagara Falls, N.Y.) under the trade designationNiaproof 08, which contains 38.5 to 40.5% sodium 2-ethylhexyl sulfateand the balance water. Alternatives include sodium tetradecyl sulfateavailable from Niacet under the trade designation Niaproof 4, sodiumlauryl sulfate available from Stepan Company (Northfield, Ill.) underthe trade designation Polystep B-5, and sodium n-decyl sulfate availablefrom Henkel Corporation/Emery Group, Cospha/CD of (Ambler, Pa.) underthe trade designation Sulfotex 110. The addition of a sulfated anionicsurfactant compound surprisingly permits the acidity level to be raised,without the expected detrimental effect of lightening the coating.Because the acidity level can be raised in this manner, copper loadingis increased. It also helps darken the coating. This compound is presentin this embodiment in a concentration sufficient to increase copperloading without substantial lightening of the coating. The typicalconcentration is at least about 0.001%, and preferably at least about0.1%. The concentration of sulfated anionic surfactant is no greaterthan about 10%, and preferably no greater than about 5%. One preferredrange is between about 0.05 and 2%. In one preferred embodiment thesulfated anionic surfactant concentration is about 0.5%. In another itis 0.15%.

In a currently preferred embodiment, the composition also includes oneor more ethoxylated phenol derivatives as a nonionic surfactant. Thissurfactant has been discovered to provide the unexpected additionalbenefit of improving peel strength. In one preferred embodiment, thissurfactant is one or more ethoxylated nonylphenols, such aspolyoxyethylene nonylphenol. Polyoxyethylene nonylphenol is availablefrom Dow Chemical Company (Midland, Mich.) under the trade designationTergitol NP9. Alternatives include an ethoxylated nonylphenol availablefrom Dow Chemical Company under the trade designation Tergitol NP8,nonylphenoxypolyethoxyethanol available from Union Carbide Corporation(Danbury, Conn.) under the trade designation Triton N, and ethoxylatednonylphenol (or nonoxynol-2) available from Rhone-Poulenc, Surfactant &Specialty Division of New Jersey under the trade designation IgepalCO-210.

The concentration of this surfactant is selected to be sufficient toimprove peel strength. One currently preferred embodiment includes atleast about 0.0001% of an ethoxylated phenol derivative. As a generalproposition, the concentration is at least about 0.01%, preferably atleast about 0.2%; and is less than about 10%, preferably less than about5%. One preferred range is between about 0.0001% and about 2%, such asbetween about 0.01% and about 1%, such as from about 0.02% to about 1%.

In another currently preferred embodiment, the composition comprises oneor more quaternary amine surfactants. In one preferred embodiment, thissurfactant is polyethoxylated quaternary amine Exemplary suchsurfactants include the TOMAH quats including: TOMAH Q-14-2 (a 74%active isodecyloxypropyl bis-(2-hydroxyethyl)methyl ammonium chloride),TOMAH Q-17-2 (a 74% active isotridecyloxypropylbis-(2-hydroxyethyl)methyl ammonium chloride), TOMAH Q-17-5 (a 74%active isotridecyloxypropyl poly(5)oxyethylene methyl ammoniumchloride), TOMAH Q-18-2 (a 50% active octadecylbis-(2-hydroxyethyl)methyl ammonium chloride), TOMAH Q-S (50% or 80%active mono soya methyl ammonium chloride). TOMAH Q-DT (50% activetallow diamine diquaternary), TOMAH Q-C-15 (a 100% activecocopoly(15)oxyethylene methyl ammonium chloride), and TOMAH Q-ST-50 (a50% active trimethyl stearyl ammonium chloride). In a preferredembodiment, the surfactant is TOMAH Q-14-2 (a 74% activeisodecyloxypropyl bis-(2-hydroxyethyl)methyl ammonium chloride) added tothe composition in a concentration between about 0.05% and about 5%,such as between about 0.1% and about 2%, such as about 1%.

The composition further includes a source of halide ions, preferably asource of chloride ions. The source may be NaCl or HCl, and provides achloride ion concentration in the range of about 10 to 100 ppm. The mostpreferred range for one embodiment is between about 60 and 65 ppm.Preferred ranges are different for other embodiments depending on theoverall composition and application. This increased Cl⁻ level incomparison to previous formulations helps to increase the ratio ofcuprous copper to cupric copper, which has been discovered to increasepeel strength and lengthen the total time to delaminate. The Cl⁻ leveltapers off and then stabilizes during use of the composition. As such,an initial Cl⁻ ion concentration of between about 20 ppm and about 100ppm is preferred in one embodiment in order to achieve a Cl⁻ ion contentin service of on the order of about 20 to 80 ppm.

The composition may additionally comprise transition metal ions, such asZn²⁺ and Ni²⁺. It is believed that transition metal ions enhance thermalresistance of the organometallic conversion coating. Exemplary sourcesof Zn²⁺ and Ni²⁺ include zinc iodide and nickel iodide, but other watersoluble sources may be used as well, such as zinc acetate and nickelacetate. In addition to providing the transition metals, these sourcesprovide halide ion. The source of transition metal ion may be added tothe composition to provide between about 10 g/L and about 0.1 g/Ltransition metal ion.

The adhesion promotion composition is manufactured by mixing thecomponents in an aqueous solution, preferably using deionized water. Ina preferred embodiment, the solution further comprises an alcohol toenhance the solubility of the organic components. In accordance withstandard safe practice, hydrogen peroxide is added to the composition ina diluted form.

The copper surface is contacted with the adhesion promotion compositiongenerally without any pre-treatment. The copper surface may havepreviously been provided with a tarnish-inhibiting coating, e.g., byincorporating the tarnish inhibitor into a resist stripping compositionused in an immediately preceding step of etch resist stripping. Tarnishinhibitors used in such strippers are, for example, a triazole or othercoating. If so, it may be desirable to pre-clean the copper surfacebefore contact with the composition. Pre-cleaning solutions includeacidic pre-cleaners such as PC 7077 (available from Enthone Inc. of WestHaven, Conn.), prepared and used according to the manufacturer'sinstructions. For example, in one embodiment, the copper surface may bepre-cleaned using a commercially available acidic pre-cleaner at atemperature between about 30° C. and about 50°, such as between about30° C. and about 40° C. for a duration between about 30 seconds andabout 3 minutes, such as between about 45 seconds and about 2 minutes.Cleaning with the acidic pre-cleaner is preferably followed by a rinsewith distilled water.

Acidic pre-cleaning is preferably followed by alkaline cleaning, such asPC 7086 or PC 7096 (available from Enthone Inc. of West Haven, Conn.),prepared and used according to the manufacturer's instructions. Forexample, in one embodiment, the copper surface may be cleaned using acommercially available alkaline pre-cleaner at a temperature betweenabout 40° C. and about 60°, such as between about 45° C. and about 54°C. for a duration between about 20 seconds and about 2 minutes, such asbetween about 30 seconds and about 1 minute. Cleaning with the alkalinepre-cleaner is preferably followed by a rinse with distilled water.

Preferably, prior to contact with the adhesion promotion composition,the copper surface will be substantially dry or have only minimalwetness. Apart from such a cleaning step, it is generally unnecessary tocarry out any pre-treating steps. In a preferred embodiment of theinvention, the adhesion promotion step follows immediately after an etchresist stripping step or there is a single pre-cleaning step between theetch resist stripping step and the adhesion promotion step.

Contact with the adhesion promotion composition may be by anyconventional means, for example by immersion in a bath of the adhesionpromotion composition or by spraying or any other means of contact.Contact may be as part of a continuous process. As is well understood inthe art, immersion processes involve simply dipping the substrate into abath of the composition for the desired period. Spray processestypically involve application using a series of automated squeegee-typemechanisms. The method of application is not critical to the invention.However, the tolerance for copper loading can be greater for sprayprocesses than for dip processes because, for example, there is morebath stagnation with dip processes.

Contact of the copper surface with the adhesion promotion composition istypically at a temperature between about 20° C. and about 40° C., thoughtemperatures reasonably outside this range are operable. The contacttime is generally no less than 1 second, preferably no less than 5seconds, and often at least 10 seconds, most preferably at least 30seconds. The maximum contact time may be up to 10 minutes, althoughpreferably the contact time is no greater than 5 minutes, mostpreferably no greater than 2 minutes. A contact time of about 1 minuteor less than 1 minute is standard. If the contact time of the adhesionpromotion composition with the copper surface is too long, there is arisk that the copper surface may be etched away due to dissolutionand/or that a deposit other than the micro-porous crystalline depositthat forms the micro-roughened surface will be deposited onto thesurface of the conducting material.

After contact of the copper surface with the adhesion promotioncomposition to form the micro-roughened surface, generally a pre-preginsulating layer may be placed directly adjacent to the copper surfaceand the pre-preg insulating layer adhered directly to the copper surfacein the adhesion step, forming a multi-layer PCB. Generally, in theadhesion step, heat and pressure are applied to initiate the adhesionreaction. In the adhesion step, mechanical bonding is due to penetrationof the polymeric material of the insulating layer into themicro-roughened surface provided in the adhesion promotion step.According to the method of the present invention, the second functionalgroup of the multi-functional compound may also chemically bond to theorganic material and/or glass fiber present in the pre-preg insulationlayer, providing enhanced adhesive strength. Although it may bedesirable to follow the adhesion promotion step with a speciallyformulated rinse step, it is often adequate to rinse just with water.

A pre-preg insulating layer is applied directly to the micro-roughenedsurface, i.e., preferably without any intermediate metal deposition ontothe micro-roughened surface or the like, although optionally with apost-treatment cupric oxide removal or reduction operation to furtherenhance the bond strength as disclosed in U.S. Pat. No. 6,294,220.Pressure is applied by placing the layers that are to form themulti-layer laminate of the PCB in a press. Where pressure is applied itis generally from 100 to 400 psi, preferably from 150 to 300 psi. Thetemperature of this adhesion step will generally be at least about 100°C., preferably between about 120° C. and about 200° C. The adhesion stepis generally carried out for any period from 5 minutes to 3 hours, mostusually from 20 minutes to 1 hour, but is for sufficient time andpressure and at a sufficiently high temperature to ensure good adhesionbetween the first and second layers. During this adhesion step, thepolymeric material of the insulating layers, generally an epoxy resin,tends to flow ensuring that the conductive pattern in the metal issubstantially sealed between insulating layers, so subsequentpenetration of water and air is avoided. Several layers may be placedtogether in the adhesion step to effect lamination of several layers ina single step to form the MLB.

Though the exemplary arrangement discussed at length herein is apre-preg insulating layer adhered to a copper surface, the inventionalso includes improving adhesion of other dielectric materials, whetherpermanent or temporary, to copper. For example, the invention improvesadhesion between copper and a solder mask that is dielectric. Itsimilarly improves copper adhesion with inks, polymeric photo-resists,and dry films. It also has application in connection with photoimageabledielectrics or other dielectrics used in the context of high densityinterconnect and sequential build up technologies.

In one form the invention is a ready-to-use adhesion promotioncomposition that can be used directly for immersion or other exposure ofthe substrate. In another form the invention is a concentrate that is tobe diluted to form the composition for immersion or other exposure.

The following examples further illustrate the practice of the presentinvention.

EXAMPLES Example 1 Adhesion Promotion Composition

An adhesion promotion composition comprising a multi-functional azolewas prepared having the following components:

6-benzylamino-purine (1.0 g)

Ethylene glycol butyl ether (200 mL)

ZnI₂ (1.0 g)

Water (to 1 L).

The composition was prepared according to the following protocol:

1) 6-benzylamino-purine (1.0 g) dissolved in ethylene glycol butyl ether(200 mL).

2) Water (500 mL) added.

3) Homogenized solution.

4) Zinc iodide (1.0 g) dissolved in solution.

5) Water added to solution volume of 1.0 liter.

Example 2 Adhesion Promotion Composition

An adhesion promotion composition comprising a multi-functional azolewas prepared having the following components:

6-benzylamino-purine (1.0 g)

Ethylene glycol butyl ether (200 mL)

NiI₂ (1.0 g)

Water (to 1 L).

The composition was prepared according to the protocol described inExample 1, except that NiI₂ was added instead of ZnI₂.

Example 3 Treatment of Pre-Treated Copper Samples with AdhesionPromotion Composition

Two copper test coupons were pre-treated with acid cleaning (PC1010) andmicroetching (ME 1020) compositions available from Enthone Inc. (WestHaven, Conn.) The copper test coupons then treated with the adhesionpromotion compositions of Examples 1 and 2 by dipping one coupon in eachcomposition for 1 minute at room temperature. This treatment forms afilm comprising the multi-functional compounds of Examples 1 and 2 overthe surface of the copper test coupons.

Example 4 Wetting Balance Tests

After the test coupons were treated with the adhesion promotioncompositions according to the method of Example 3, the resistance of theadhesion promotion films on the copper coupons to acid and flux wastested by applying solder and flux and passing the coupons through areflow process. Pb-free solder was applied to the copper coupons.

The flux applied was EF8000 flux available from AlphaMetal Inc. (JerseyCity, N.J.). The Pb-free solder was reflowed over the copper testcoupons at a peak reflow temperature of 262° C.

Copper discoloration was minor after passing 1× lead-free reflow. Thecoating applied from the composition of Example 1 was thinner than thecoating applied from the composition of Example 2, but both coatingswere on the order of about 0.1 μm.

The reflowed copper samples having adhesion promotion compositions ofExamples 1 and 2 applied thereon were subjected to wetting balancetests.

FIGS. 1 and 2 are graphs showing the results of the wetting balancetests. Due to acid resistance, the coating from the composition ofExample 2, FIG. 2, showed a dewetting curve, which means that theorganometallic coating was not stripped by the flux and had good acidresistance.

Example 5 X-Ray Photoelectron Spectroscopy on Coated Copper Samples

The extent of copper oxidation on the copper coupons treated accordingto the method of Example 4 before and after reflow was determined byX-ray photoelectron spectroscopy (XPS). FIG. 3 shows XPS spectra of theregion from 920 to 965 eV which are useful for determining the oxidationstate of copper on the surface of the treated coupons. The slight CuOpeak indicates that there is traceable CuO formed after one lead-freereflow (peak temperature is 262° C.), which is from the oxidation ofcopper during reflow processing. In a non-treated coupon, the extent ofoxidation would be much greater and the CuO peak would be very high.

Table III is a chart of the quantitative results of XPS analysis of thecoating applied from the compositions of Examples 1 and 2, before andafter reflow. The chart shows the atomic % of each elements present inthe coating. The atomic % of N is not reduced much after reflow.Accordingly, it is believed that amino present in the multi-functionalazole molecule after reflow is available for chemical bonding to organicmaterial in the pre-preg insulating layer.

TABLE III Atomic Composition of Coatings C Cu I N O Ni Zn Example 1(Pre- 65.3 5.7 1.5 20.0 6.0 1.5 reflow) Example 1 (Post- 61.2 8.3 1.517.8 9.5 1.7 reflow) Example 2 (Pre- 62.4 6.6 2.9 21.5 6.3 0.3 reflow)Example 2 (Post- 56.5 11.6 4.0 18.5 9.1 0.3 reflow)

Example 6 Adhesion Promotion Composition

The following adhesion promoting composition was prepared:

-   -   TOMAH solution (10 mL, TOMAH Q-14-2, available from TOMAH        Products, Inc., Milton, Wis.)    -   NaCl solution (5 mL)    -   H₂SO₄ (96% solution, 105.5 g)    -   Mixture of benzotriazole-4-carboxylic acid and        benzotriazole-5-carboxylic acid (3.8 g)    -   H₂O₂ (35% solution, 150 mL)    -   Water to approximately 1.15 L.

This composition may be prepared according to the following protocol:

-   -   1) Mixture of benzotriazole-4-carboxylic acid and        benzotriazole-5-carboxylic acid (3.8 g) dissolved in sulfuric        acid (105.5 g).    -   2) Water (400 mL) added.    -   3) Homogenized solution.    -   4) TOMAH solution (10 mL), NaCl solution (5 mL), and hydrogen        peroxide (150 mL) added in order.    -   5) Water added to the total volume is 1.15 liter.

Example 7 Treatment of Pre-Treated Copper Samples with AdhesionPromotion Composition

A copper panel was processed using the adhesion promoting composition ofExample 6 according to the following protocol

-   -   1) Copper panel pre-treated in Microetch PC5760 (from Enthone        Inc.) at 25° C. for 30 seconds.    -   2) Rinsed with D.I. water.    -   3) Copper panel dipped in Alkaline Cleaner PC-7047 (from Enthone        Inc.) at 45° C. for 40 seconds.    -   4) Rinsed with D.I. water.    -   5) Copper panel dipped in the adhesion promotor composition of        Example 6 at 32° C. for 3 minutes.

After the treatment, the copper coupon was processed through laminationprocedure to determine the peel-off strength. The peel-off strength is0.193 N/mm.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

When introducing elements of the present invention or the preferredembodiment(s) thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

As various changes could be made in the above without departing from thescope of the invention, it is intended that all matter contained in theabove description and shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

1. An adhesion promotion composition for enhancing adhesion between acopper conducting layer and a dielectric material during manufacture ofa printed circuit board, the adhesion promotion composition comprising:a multi-functional compound comprising a first functional group and asecond functional group, wherein (1) the first functional group isselected from the group consisting of an aromatic heterocyclic compoundcomprising nitrogen and an aliphatic amine, and (2) the secondfunctional group is selected from the group consisting of vinyl ether,amide, thiamide, amine, carboxylic acid, ester, alcohol, silane, alkoxysilane, and combinations thereof; a surfactant; and an acid.
 2. Theadhesion promotion composition of claim 1 wherein the aromaticheterocyclic compound comprising nitrogen is an azole. 3-7. (canceled)8. The adhesion promotion composition of claim 1 wherein themulti-functional compound has structure (Ia) or structure (Ib):

wherein: A₁, A₂, A₃, A₄, A₅, A₆, and A₇ are carbon atoms or nitrogenatoms and the sum of nitrogen atoms from A₁, A₂, A₃, A₄, A₅, A₆, and A₇is 0, 1, 2, or 3; A₁₁, A₂₂, A₃₃, A₄₄, A₅₅, A₆₆, and A₇₇ are selectedfrom the group consisting of electron pair, hydrogen, substituted orunsubstituted alkyl, substituted or unsubstituted aryl, substituted orunsubstituted vinyl ether, substituted or unsubstituted amide,substituted or unsubstituted amine, substituted or unsubstitutedcarboxylic acid, substituted or unsubstituted ester, substituted orunsubstituted alcohol, and substituted and unsubstituted silane oralkoxysilane; and at least one of A₁₁, A₂₂, A₃₃, A₄₄, and A₅₅ isselected from the group consisting of substituted or unsubstituted vinylether, substituted or unsubstituted amide, substituted or unsubstitutedamine, substituted or unsubstituted carboxylic acid, substituted orunsubstituted ester, substituted or unsubstituted alcohol, andsubstituted and unsubstituted silane or alkoxysilane.
 9. The adhesionpromotion composition of claim 8 wherein the structure of themulti-functional compound is selected from the group consisting ofstructure (II), structure (III), and structure (IV):

wherein A₂₂, A₄₄, A₅₅, A₆₆, and A₇₇ are as defined in connection withstructures (Ia) and (Ib).
 10. The adhesion promotion composition ofclaim 1 wherein the multi-functional compound has structure (V):

wherein: A₂, A₃, A₄ and A₅ are carbon atoms or nitrogen atoms and thesum of nitrogen atoms from A₂, A₃, A₄ and A₅ is 0, 1 or 2; A₂₂, A₃₃,A₄₄, and A₅₅ are selected from the group consisting of hydrogen,substituted or unsubstituted alkyl, substituted or unsubstituted aryl,substituted or unsubstituted vinyl ether, substituted or unsubstitutedamide, substituted or unsubstituted amine, substituted or unsubstitutedcarboxylic acid, substituted or unsubstituted ester, substituted orunsubstituted alcohol, and substituted and unsubstituted silane oralkoxysilane; and at least one of A₂₂, A₃₃, A₄₄, and A₅₅ is selectedfrom the group consisting of substituted or unsubstituted vinyl ether,substituted or unsubstituted amide, substituted or unsubstituted amine,substituted or unsubstituted carboxylic acid, substituted orunsubstituted ester, substituted or unsubstituted alcohol, andsubstituted and unsubstituted silane or alkoxysilane. 11-32. (canceled)33. A method for enhancing adhesion between a copper conducting layerand a dielectric material during manufacture of a printed circuit board,the process comprising: exposing the copper conducting layer to anadhesion promotion composition comprising a multi-functional compoundcomprising a first functional group and a second functional group,wherein (1) the first functional group is selected from the groupconsisting of an aromatic heterocyclic compound comprising nitrogen andan aliphatic amine, and (2) the second functional group is selected fromthe group consisting of vinyl ether, amide, thiamide, amine, carboxylicacid, ester, alcohol, silane, alkoxy silane, and combinations thereof,wherein the first functional group interacts with the surface of thecopper conducting layer to form a copper(I) rich organometallic adhesivefilm over the surface of the copper conductive substrate.
 34. The methodof claim 33 further comprising the step of applying the dielectricmaterial to the copper conducting material having the copper(I) richorganometallic adhesive film thereon, wherein the second functionalgroup reacts with the dielectric material to form a chemical bondbetween the multi-functional compound and the dielectric material. 35.The method of claim 33 wherein the aromatic heterocyclic compoundcomprising nitrogen is an azole.
 36. The method of claim 35 wherein theazole comprises at least one nitrogen atom bonded to an acidic hydrogenatom.
 37. The method of claim 33 wherein the second functional group isbonded to a carbon atom of the aromatic heterocyclic compound comprisingnitrogen.
 38. The method of claim 33 wherein the second functional groupis bonded to a nitrogen atom of the aromatic heterocyclic compoundcomprising nitrogen and the aromatic heterocyclic compound comprisingnitrogen comprising at least one other nitrogen atom bonded to an acidichydrogen atom.
 39. (canceled)
 40. The method of claim 33 wherein thearomatic heterocyclic compound comprising nitrogen interacts withcopper(I) ions on the surface of the copper conducting layer andcopper(II) ions in solution in a manner sufficient to form a filmcomprising copper(I)-based organometallics on the surface of the copperconducting layer, the film thereby increasing the ratio of copper(I)ions to copper(II) ions on the surface of the copper conducting layer.41. The method of claim 33 wherein the multi-functional compound hasstructure (Ia) or structure (Ib):

wherein: A₁, A₂, A₃, A₄, A₅, A₆, and A₇ are carbon atoms or nitrogenatoms and the sum of nitrogen atoms from A₁, A₂, A₃, A₄, A₅, A₆, and A₇is 0, 1, 2, or 3; A₁₁, A₂₂, A₃₃, A₄₄, A₅₅, A₆₆, and A₇₇ are selectedfrom the group consisting of electron pair, hydrogen, substituted orunsubstituted alkyl, substituted or unsubstituted aryl, substituted orunsubstituted vinyl ether, substituted or unsubstituted amide,substituted or unsubstituted amine, substituted or unsubstitutedcarboxylic acid, substituted or unsubstituted ester, substituted orunsubstituted alcohol, and substituted and unsubstituted silane oralkoxysilane; and at least one of A₁₁, A₂₂, A₃₃, A₄₄, and A₅₅ isselected from the group consisting of substituted or unsubstituted vinylether, substituted or unsubstituted amide, substituted or unsubstitutedamine, substituted or unsubstituted carboxylic acid, substituted orunsubstituted ester, substituted or unsubstituted alcohol, andsubstituted and unsubstituted silane or alkoxysilane.
 42. The method ofclaim 41 wherein the structure of the multi-functional compound isselected from the group consisting of consisting of structure (II),structure (III), and structure (IV):

wherein A₂₂, A₄₄, A₅₅, A₆₆, and A₇₇ are as defined in connection withstructures (Ia) and (Ib).
 43. The method of claim 33 wherein themulti-functional compound has structure (V):

wherein: A₂, A₃, A₄ and A₅ are carbon atoms or nitrogen atoms and thesum of nitrogen atoms from A₂, A₃, A₄ and A₅ is 0, 1 or 2; A₂₂, A₃₃,A₄₄, and A₅₅ are selected from the group consisting of hydrogen,substituted or unsubstituted alkyl, substituted or unsubstituted aryl,substituted or unsubstituted vinyl ether, substituted or unsubstitutedamide, substituted or unsubstituted amine, substituted or unsubstitutedcarboxylic acid, substituted or unsubstituted ester, substituted orunsubstituted alcohol, and substituted and unsubstituted silane oralkoxysilane; and at least one of A₂₂, A₃₃, A₄₄, and A₅₅ is selectedfrom the group consisting of substituted or unsubstituted vinyl ether,substituted or unsubstituted amide, substituted or unsubstituted amine,substituted or unsubstituted carboxylic acid, substituted orunsubstituted ester, substituted or unsubstituted alcohol, andsubstituted and unsubstituted silane or alkoxysilane.
 44. The method ofclaim 33 wherein the second functional group is the vinyl ether.
 45. Themethod of claim 44 wherein the first functional group is selected fromthe group consisting of benzimidazole, indazole, imidazole, andtriazole.
 46. The method of claim 44 wherein the multi-functionalcompound is selected from the group consisting of2-(vinyloxy)-1H-benzimidazole, 2-(vinyloxymethyl)-1H-benzimidazole,3-(vinyloxy)-2H-indazole, 2-(vinyloxy)-1H-imidazole,2-(vinyloxymethyl)-1H-imidazole, and 3-(vinyloxy)-1H-1,2,4-triazole. 47.The method of claim 33 wherein the second functional group is the amine.48. The method of claim 47 wherein the first functional group isselected from the group consisting of purine, benzotriazole,benzimidazole, imidazole, and pyrazole
 49. The method of claim 47wherein the multi-functional compound is selected from the groupconsisting of 6-phenylamino-purine, 6-benzylamino-purine,6-methylamine-purine, 6-dimethyl-purine, 9H-purine-2,6-diamine,α-methyl-N-phenyl-1H-benzotriazole-1-methanamine,2-(2-aminoethyl)benzimidazole, 2-(2-aminophenyl)-1H-benzimidazole,histamine, 1-methylhistamine, 3-methylhistamine,1-(3-aminopropyl)imidazole, and 3-amino-pyrazole.
 50. The method ofclaim 33 wherein the second functional group is the amide or thethiamide. 51-62. (canceled)
 63. The method of claim 62 wherein the firstfunctional group is selected from the group consisting of benzotriazoleand imidazole.
 64. The method of claim 62 wherein the multi-functionalcompound is selected from the group consisting of1-(trimethylsilyl)-1H-benzotriazole,1-[(trimethylsilyl)methyl]benzotriazole, 1-(trimethylsilyl)imidazole,and 1-(tert-butyldimethylsilyl)imidazole.